1. Field of the Invention
The present invention relates to a rubber composition which is useful for preparing products such as a rubber hose, a gasket and packing material, and to material for the rubber composition.
2. Description of the Related Art
It have been known to add a layered mineral filler such as clay or mica in the form of flat to a rubber to mix them in order to improve gas-barrier properties of the rubber. The layered mineral filler in the form of flat is not permeable to gas, and therefore it is generally considered that the gas-barrier properties of the rubber composition can be improved by the volume fraction of the filler mixed with the rubber.
Even the use of the layered mineral filler is restricted in the improvement of the gas-barrier properties. In contrast, increase of the added amount of the layered mineral filler brings about deterioration of processing properties (e.g., extruding properties) of a formulation for the rubber composition and increase of the weight of the formulation, and further leads to lowering of strength and elongation of the resultant rubber composition.
JP-A-11-159667 describes a process for preparing a rubber composition by using an organic-treated clay and a modified butyl rubber having a carboxylic anhydride group. Further it describes that a hose for transporting refrigerant is obtained by use of the rubber composition and the hose has excellent vibration absorbing properties and fluid-barrier hose has excellent vibration absorbing properties and fluid-barrier properties. The organic-treated clay (clay treated with organic compound) is obtained by ionicically combining a clay with an organic onium ion. Examples of the organic onium ion include ammonium ion having six or more carbon atoms such as hexyl ammonium ion, stearyl ammonium ion and trioctyl ammonium ion.